1. Linux Networks TCP/IP Networking Layers BSD Socket Interface
INET Socket Layer
Create
Bind
Listen
Accept
Connect

2. Linux Networking Layers
Network Applications
User
Kernel
BSD Sockets
Socket Interface
INET Sockets
TCP
UDP
Protocol Layers IP
ARP
Network Devices
PPP
SLIP
Ethernet
Linux Networking Layers

3. Linux BSD Socket Data Structure
files_struct
count
close_on_exec
open_fs
fd[0]
fd[1]
fd[255]
BSD Socket
File Operations
file
f_mode
f_pos
f_flags
f_count
f_owner
f_op
f_inode
f_version
lseek
read
write
select
ioctl
close
fasync
inode
socket
SOCK_STREAM
type
protocol
data
Address Family
socket operations
SOCK_STREAM
sock
type
protocol
socket
Linux BSD Socket Data Structure

4. System Call <net/socket.c>
int sys_socketcall(int call, unsigned long *args);
call
<linux/net.h>
SYS_SOCKET --> socket()
SYS_BIND > bind()
args
args[]

5. family <include/linux/socket.h> AF_UNIX AF_INET AF_IPX
Unix domain sockets
AF_INET
Internet IP Protocol
AF_IPX
Novell IPX
AF_APPLETALK
Appletalk DDP
AF_X25
Reserved for X.25 project

6. type <include/linux/socket.h> SOCK_STREAM SOCK_DGRAM SOCK_RAW
stream (connection) socket
SOCK_DGRAM
datagram (conn.less) socket
SOCK_RAW
raw socket
SOCK_RDM
reliably-delivered message
SOCK_SEQPACKET
sequential packet socket

7. protocol <include/linux/in.h> IPPROTO_IP IPPROTO_ICMP
Dummy protocol for TCP
IPPROTO_ICMP
Internet Control Message Protocol
IPPROTO_IGMP
Internet Group Management Protocol
IPPROTO_TCP
Transmission Control Protocol
IPPROTO_EGP
Exterior Gateway Protocol

8. socket(family, type, protocol)
<net/socket.c>
sys_socket(...)
get an empty inode for socket structure
allocate a sock structure
return the file descriptor of the socket if success

9. bind(fd, uaddr, addrlen)
<net/socket.c>
sys_bind(...)
bind a name to a socket
move the socket address to kernel space
address & port checking

10. listen(fd, backlog) <net/socket.c> sys_listen(...)
allow the protocol to do anything necessary
move a socket into listening state

11. accept(fd, sockaddr, skaddrlen)
<net/socket.c>
sys_accept(...)
attempt to create a new socket
set up the link with the client
wake up the client
return the new fd

12. connect(fd, uaddr, addrlen)
<net/socket.c>
sys_connect(...)
attempt to connect to a socket with the server address
move the address to kernel space